BibDocFile: CERN AFS awareness

• Introduces awareness of the CERN AFS filesystem and tools availability so that, when new g-directories are about to be allocated to host new files handled by the BibDocFile module, the special CERN AFS tools could be exploited to allocate on the fly new volumes and mount-points with the appropriate pattern and initial quota.

• Introduces new CFG_BIBDOCFILE_AFS_VOLUME_PATTERN and CFG_BIBDOCFILE_AFS_VOLUME_QUOTA configuration parameters that are considered only when either CFG_CERN_SITE or CFG_INSPIRE_SITE is set to 1. (closes #1388)

Reported-by: Jan Aage Lavik <jan.age.lavik@cern.ch>